Much effort has been expended in discovering and developing useful fire retardant polymer composition systems, and numerous examples of fire retardant polymers have appeared in the literature and some of them are in commercial use. But, the fire retardant requirements for polymeric materials have become evermore stringent as technology has become more sophisticated. Thus, whereas low burning rates were once the sole objective of research for fire retardant polymers, now low smoke generation and char formation characteristics are also significant.
Concurrently, there has been a desire on the part of plastics fabricators to retain the other beneficial qualities of the base polymer while enhancing the fire retardant properties. But heretofore, efforts to impart fire retardancy to polymer systems has resulted in diminishing the other useful properties. Thus, normally translucent polyester resins have been rendered opaque by the incorporation of sufficient quantities of antimony trioxide to render the polyester resins sufficiently fire retardant for certain uses.
Accordingly, it is an object of this invention to provide superior fire retardant unsaturated polyester resins that not only have low burning rates, but also exhibit low smoke generation when in contact with a flame.
It is also an object of the invention to provide superior fire retardant polyester resins that develop a beneficial, insulating layer of char in the presence of a flame which inhibits further combustion of the polymer.
It is still another object of the invention to render unsaturated polyester resins fire retardant without diminishing or deteriorating other useful properties of the polymer system.
These and other objects are accomplished by this invention which is described in detail hereinafter.